Exhibit Hall | Forum 4
Purpose: Total scalp irradiation (TSI) for angiosarcoma presents major technical and dosimetric challenges due to large, irregular, and superficial spread of a complex target. To increase superficial coverage, spare normal brain, and eliminate the difficulty of patient set-up/fields-matching, we propose two novel irradiation techniques: HyperArc VMAT or co-planar Halcyon RDS utilizing a 3D-printed 1 cm scalp bolus.
Methods: Ten previously treated TSI patients were selected. HyperArc plans utilized 6MV-FFF beam (800MU/min) on TrueBeam with fully-automated HyperArc module and 3D-printed 1 cm bolus delivering 70 Gy in 35 fractions. Plans were re-created using 4 full-arcs on Halcyon equipped with 6MV-FFF beam (800MU/min) with lower mean-energy of 1.3MeV and maximal dose at 1.3cm. Similar planning parameters were used on both platforms. Plan quality, treatment delivery accuracy and efficacy was evaluated.
Results: Both platforms provided highly conformal and homogenous TSI plans, showing statistically insignificant differences on mean target dose, conformity, and dose homogeneity. Average mean target BED10 was 92.6±1.5Gy (HyperArc) vs 94.4±0.8Gy (Halcyon)(p=0.065). HyperArc provided mean brain dose (MBD) and V60Gy of 8.3±1.4Gy and 0.86±0.95cc, compared to 8.6±1.45Gy(p>0.05) and 1.32±0.85cc(p=0.04), on Halcyon. For both Linacs, significant reduction of maximal dose to critical organs including hippocampi <5Gy (all, p>0.05) was found. Halcyon plan complexity slightly decreased as observed on decreases of total monitor units, modulation factor and beam-on time by 130, 0.65, and 0.7min, and overall treatment time was reduced by 2.6min; although, both platforms can deliver treatment in <15min. Portal dosimetry quality assurance of HyperArc and Halcyon plans were 99.7% and 100%, demonstrating similar delivery accuracy.
Conclusion: Both HyperArc and Halcyon can deliver an accurate and efficient treatment of >90GyBED10 to the large, and complex angiosarcoma of scalp and face with significantly lower MBD <10 Gy. TSI using these platforms is ongoing in our clinic and highly recommended to others, including community clinics.